Blind rivet setting device

ABSTRACT

A blind rivet setting device and method of operating the blind rivet setting device. The blind rivet setting device includes a housing, a pulling device that is at least partially arranged in the housing and a drive that acts on the pulling device in a pulling direction and in a reset direction oriented opposite to the pulling direction. A length of at least one of the housing and the pulling device is changeable from a first length to a second length when a predetermined force is exceeded.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119(a) ofEuropean Patent Application No. 14 158 483.9 filed Mar. 10, 2014, thedisclosure of which is expressly incorporated by reference herein in itsentirety.

BACKGROUND OF THE EMBODIMENTS

1. Field of the Invention

Embodiments of the invention relate to a blind rivet setting device witha housing, a pulling device that is at least partially arranged in thehousing, and a drive that acts on the pulling device in a pullingdirection and in a reset direction oriented opposite to the pullingdirection.

2. Discussion of Background Information

A blind rivet setting device of this type is known, e.g., from DE 41 26602 A1.

“Blind rivet setting device” is to be understood below as meaning adevice that can be used to set blind rivets, blind rivet nuts, and blindrivet fasteners generally. To set a blind rivet fastener of this type, apulling mandrel of the blind rivet fastener is inserted into the housingthrough a front-face opening. The blind rivet fastener is then guidedthrough an opening in a component until the set head of the fastenerbears against the component. When the drive of the pulling device isactuated in the pulling direction, the pulling mandrel of the pullingdevice is gripped and pulled in the pulling direction. The housingpresses the set head against the component. As a result, a closing headforms on the side of the component facing away from the set head. Whenthe closing head is formed and the setting operation is thus virtuallycomplete, the drive drives the pulling device in the reset direction sothat the device is once again moved in the direction towards thefront-face opening of the housing. The pulling mandrel can then beremoved from the housing and the pulling device, and the blind rivetsetting device is available for a new setting operation.

To achieve a highest possible productivity, it is desirable to have themovement of the pulling device during a setting operation and also thereset movement of the pulling device proceed as quickly as possible. Thedrive is therefore embodied or formed in an adequately powerful manner.To automatically control the movement, especially the reset movement ofthe pulling device, one or multiple sensors are used.

The movement of the pulling device in the reset direction must occurwith a certain precision. If the pulling device is not moved far enoughin the reset direction, then a gripping device may not be opened farenough to remove a broken-off pulling mandrel or to allow a new pullingmandrel to be inserted. However, if the pulling device is moved too far,then it can damage the housing.

Even with a control that guides the movement of the pulling device withthe necessary precision, problems can occur. These problems result, forexample, in that abrasion debris can be produced during the setting of ablind rivet fastener, which debris accumulates between the housing andthe pulling device. A veritable “plug” can form here. If the pullingdevice is then moved back into its initial position, then the forceapplied to the housing by the drive via the pulling device and the plugcan be large enough that damage results in turn, especially to thehousing.

SUMMARY OF THE EMBODIMENTS

Accordingly, embodiments of the invention reduce the risk of damage.

A blind rivet setting device of the type named at the outset includes ahousing and/or a pulling device that can be changed between a firstlength and a second length in the reset direction after a predeterminedforce is exceeded.

With this solution, damage is avoided in that the pulling deviceshortens its length when a predetermined force is exceeded or thehousing changes its length when a predetermined force is exceeded. Ofcourse, both measures can also be combined. By the change in length, itis possible to alleviate the problem that would otherwise occur duringthe reset movement as a result of the application of an exceedinglylarge force between the housing and the pulling device. If, during thereset movement of the pulling device, a situation occurs, e.g., due tothe aforementioned plug, in which the pulling device can no longer moveback into its initial position because the accumulated debris preventsthis, then no additional housing-damaging pressure is produced; rather,the pulling device is compressed or the housing is lengthened. The usercan then take measures to eliminate the problem again, e.g., to removethe debris. In the pulling direction, however, the length is unchanged,i.e., precisely the desired kinematics, i.e., the interaction betweenthe housing and the pulling device that results in the formation of theclosing head of the blind rivet fastener, occur during a movement of thepulling device in the pulling direction.

Preferably, the pulling device has clamping jaws that are loaded into achuck housing by a compression spring. The further the clamping jaws aremoved into the chuck housing, the more closely they approach oneanother. The compression spring is thus used to produce a clamping forcewith which the clamping jaws can grip a pulling mandrel that has beenslid into the pulling device. The functioning of the compression springremains uninfluenced by the possibility of the change in length.

Preferably, the housing includes a nose piece. In a resting state, theclamping jaws are displaced into an opened position by the nose piece ifthe first length is present and are not displaced into the openedposition if the second length is present. The clamping jaws aretypically arranged in a chuck housing which, when it acts on theclamping jaws in the pulling direction, moves the clamping jaws towardsone another perpendicular to the pulling direction, so that the clampingjaws can hold in place a pulling mandrel of a blind rivet fastener. Theclamping jaws are thereby usually pressed into the chuck housing by theforce of a spring. The nose piece projects into the chuck housing whenthe pulling device is located in its initial position, i.e., in theposition moved furthest in the reset direction, so that the clampingjaws have been slid back a small distance in the chuck housing and arethus located in an “opened position,” in which a pulling mandrel can beremoved from the clamping jaws or inserted into the clamping jaws. Iffouling or contamination of the type described accumulates between thehousing and the pulling unit, the embodiment described has the advantagethat the user of the blind rivet setting device is alerted to a need formaintenance. If it is no longer possible to insert a pulling mandrel ofa blind rivet fastener into the pulling device through the front-faceopening, it is a natural reaction for the user to assume that fouling orthe like is present. In this case, partial disassembly of the housingwill enable the removal of the fouling. In this manner, the problem isessentially solved. In many cases, the user is already alerted to thefault in that it is no longer possible to pull the pulling mandrel of aset blind rivet fastener out of the housing without difficulty.

Preferably, a difference between the first length and the second lengthlies within the range of 1 to 5 mm. The change in length is thusrelatively small. However, it is sufficient to prevent exceedingly largeforces from acting between the pulling device and the housing.

Preferably, the pulling device includes a first pulling element and asecond pulling element. The first pulling element and the second pullingelement are positively engaged and an elastic element acts between thefirst pulling element and the second pulling element in the resetdirection. With this embodiment, it is possible to transfer the forcenecessary to form the closing head of the blind rivet fastener from thedrive to the pulling mandrel by means of a continuous pull rod. As aresult of the positive engagement between the first pulling element andthe second pulling element, an avoidance movement is not possible. Thisis not the case, however, for a movement in the opposite direction.Here, the second pulling element acts, possibly through one or multipleadditional parts, on the first pulling element via an elastic element.Therefore, if the first pulling element reaches its limit at thehousing, for example, even with an intermediate layer of an accumulationof debris particles, then the second pulling element can move further bya compression of the elastic element.

Preferably, the elastic element is embodied or formed as a wave springwasher or other elastomeric body. The elastomeric body can, for example,be embodied or formed as a ring. A uniform resistance to a compressionthus results around the pulling device, so that the risk of the pullingdevice being deformed transversally to the pulling direction isrelatively low.

Preferably, the first pulling element includes a first step with a firstsurface directed perpendicular to the pulling direction and the secondpulling element comprises a second step with a second surface directedperpendicular to the pulling direction, wherein the elastic elementloads the first surface and the second surfaces against one another. Theterm “perpendicular” is not to be understood in the mathematically exactsense here. The two surfaces merely need to be capable of transferring aforce in the pulling direction. The pulling device thus always has itsmaximum length during a movement in the pulling direction. During amovement in the reset direction, however, the elastic element can becompressed so that the length of the pulling device can be decreased.

Alternatively or additionally, the housing includes a first housing partand a second housing part. The first housing part can be displacedrelative to the second housing part in the reset direction. With thisembodiment, the length of the housing can be extended so that even iffouling is present between the pulling device and the interior of thehousing, expressed more accurately, an inner front face of the housing,damage to the housing or the pulling device can be prevented in that thefirst housing part is displaced relative to the second housing part andthe length of the housing is thus increased.

Here, it is provided that one of the two housing parts has a markingthat is visible when the second length is present and not visible whenthe first length is present. The two housing parts are arranged so thatthey telescope into one another. Expediently, the marking is thenaffixed to the housing part that is inserted into the other housingpart.

Preferably, the first housing part and the second housing part areengaged via a locking connection. The locking connection engages whenthe first housing part is slid into the second housing part, so that thehousing then has its “target length.” At this target length, blind rivetfasteners can be set. If, during a reset movement of the pulling device,the situation occurs in which the pulling device will collide with thehousing, for example, due to a defect in a sensor, faulty programming oran accumulation of debris, then the first housing part is slid out ofthe second housing part after a force necessary to release the lockingconnection is overcome.

Preferably, the locking connection includes at least one spring elementthat is connected to one of the housing parts and engaged with the otherof the housing parts in a non-positive fit. The spring element can, forexample, engage in a groove. To release the locking connection, a forcemust be applied which presses the spring element out of the groove.

Here, it is preferred that the spring element is embodied or formed as aspring clip. A spring clip is a relatively simply designedconstructional element which can easily be used to produce a lockingconnection.

Embodiments of the invention are directed to a blind rivet settingdevice that includes a housing, a pulling device that is at leastpartially arranged in the housing and a drive that acts on the pullingdevice in a pulling direction and in a reset direction oriented oppositeto the pulling direction. A length of at least one of the housing andthe pulling device is changeable from a first length to a second lengthwhen a predetermined force is exceeded.

According to embodiments, the pulling device can include a chuck housingand clamping jaws loaded into the chuck housing by a compression spring.The housing may include a nose piece and, in a resting state, theclamping jaws are displaceable into an opened position by the nose piecewhen the length is the first length and are not displaceable into theopened position when the length is the second length.

In accordance with other embodiments, a difference between the firstlength and the second length can lie within the range of 1 to 5 mm.

According to still other embodiments, the pulling device may include afirst pulling element, a second pulling element and an elastic elementthat can be structured and arranged so that, when the pulling device isacted on in a pulling direction, the first pulling element and thesecond pulling element are positively engaged and, when the pullingdevice is acted on in the reset direction, the elastic element actsbetween the first pulling element and the second pulling element. Theelastic element may include one of a wave spring washer or otherelastomeric body. The first pulling element may include a first stepwith a first surface directed crosswise to the pulling direction and thesecond pulling element can include a second step with a second surfacedirected crosswise to the pulling direction, and the elastic element maybe arranged to load the first surface and the second surface against oneanother.

In embodiments, the housing can include a first housing part and asecond housing part that can be structured and arranged so that, in thereset direction, the first housing part can be displaced relative to thesecond housing part. One of the first and second housing parts mayinclude a marking that is visible when the second length is present andnot visible when the first length is present. The first housing part andthe second housing part may be engageable via a locking connection. Thelocking connection can include at least one spring element that may beconnected to one of the first and second housing parts and engaged withthe other of the first and second housing parts in a non-positive fit.

According to still other embodiments, the spring element may include aspring clip.

Embodiments of the invention are directed to a method of operating theabove-described blind rivet setting device. The method includes pullingthe pulling device in the driving direction to move the chuck from aninitial position to a position away from a front face of the housing,moving the pulling device in the reset direction to move the chucktoward the initial position, and, when debris in the housing preventsthe chuck from returning to the initial position, changing a length ofat least one of the pulling device and housing.

According to embodiments, the pulling device can include a first pullingelement and a second pulling element that may be structured and arrangedso that, in the driving direction, the first pulling element is engagedwith the second pulling device so that the pulling device has the firstlength, and in the reset direction, the debris causes the first pullingelement to be displaced from the second pulling element so that thepulling device has the second length. The second length can be shorterthan the first length. The pulling device may further include an elasticelement arranged to return the pulling device to the first length whenthe debris is removed.

In accordance with still yet other embodiments of the present invention,the housing may include a first housing part and a second housing partthat can be structured and arranged so that, in the driving direction,the housing has the first length, and in the reset direction, the debriscauses the first housing part to be displaceable relative to the secondhousing part so that the housing has the second length. The secondlength can be longer than the first length. The housing may furtherinclude an adjustable connection between the first housing part and thesecond housing part. The method can also include viewing a marking onthe housing to confirm that the housing has the second length.

Other exemplary embodiments and advantages of the present invention maybe ascertained by reviewing the present disclosure and the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed descriptionwhich follows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention,in which like reference numerals represent similar parts throughout theseveral views of the drawings, and wherein:

FIG. 1 shows a first embodiment of a blind rivet setting device in apartial view;

FIG. 2 shows a section D-D through a part of the blind rivet settingdevice according to FIG. 3;

FIG. 3 shows a side view of a part of a blind rivet setting device;

FIG. 4 shows a section E-E according to FIG. 2;

FIG. 5 shows a part of the blind rivet setting device in a perspectiverepresentation; and

FIG. 6 shows the part of the blind rivet setting device in an explodedview.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show structural details of the present invention in moredetail than is necessary for the fundamental understanding of thepresent invention, the description taken with the drawings makingapparent to those skilled in the art how the several forms of thepresent invention may be embodied or formed in practice.

FIG. 1 shows a part of a blind rivet setting device 1 with a housing 2that is embodied or formed as a steel sleeve in the region shown here.The housing 2 comprises a front face 3, into which a nose piece 4 isscrewed. The nose piece 4 comprises a centric opening 5, through which apulling mandrel of a blind rivet fastener can be inserted into thehousing 2.

In the housing 2, a pulling device is arranged which comprises a firstpulling element 6 and a second pulling element 7. The second pullingelement 7 is connected to a drive device 8 via a counterpart 24. In thisexemplary embodiment, drive device 8 includes a threaded spindle. In amanner known per se, the threaded spindle is connected to a threaded nutor a ball screw nut, which can be driven by an electric, pneumatic orhydraulic drive.

The first pulling element 6 acts on a chuck housing 9. In the chuckhousing 9, multiple clamping jaws 10 are arranged which are loaded intothe chuck housing 9 by a compression spring 11. Between the compressionspring 11 and the clamping jaws 10, a spacer sleeve 12 can be provided.

The chuck housing 9 comprises support surfaces 13 that are sloped to acenter axis 14. The clamping jaws 10 bear against the support surfaces13.

The chuck housing 9 can be moved in a pulling direction 15 via the twopulling elements 6, 7, the counterpart 24 and the drive device 8 inorder to set a blind rivet fastener, that is, to form a closing head onthe blind rivet fastener. The chuck housing 9 can also be moved in areset direction 16 when the setting operation is complete in order toonce again assume the initial position illustrated in FIG. 1.

In the initial position illustrated in FIG. 1, the chuck housing 9 hasbeen displaced a relatively far distance towards the front face 3 of thehousing 2 so that the clamping jaws 10 come to bear against the nosepiece 4. The clamping jaws 10 are moved slightly in the direction of thecompression spring 11 by the nose piece 4 against the force of thecompression spring 11, so that the clamping jaws can move radiallyoutwards along the support surfaces 13. As a result, an accommodationspace 17 between the clamping jaws 10 is expanded so that a pullingmandrel of a blind rivet fastener can be easily inserted or removed.

If, however, the drive device 8 moves the chuck housing 9 in the pullingdirection 15, then the clamping jaws 10 move clear of the nose piece 4and are moved radially inwards on the support surfaces 13 by thecompression spring 11, so that they can grip the pulling mandrel. Forthis purpose, the clamping jaws 10 comprise on the radial inside thereofa surface geometry 18 which improves an engagement between the clampingjaws 10 and the pulling mandrel, e.g., teeth, fluting or the like.

If the setting operation is complete, then the drive device 8 once againmoves the chuck housing 9 in the direction of the front face 3, so thatthe clamping jaws 10 open, that is, are displaced into an openedposition, and release the pulling mandrel.

The first pulling element 6 is engaged with the second pulling element 7in a positive fit in the pulling direction. For this purpose, the firstpulling element 6 comprises a first step 19, which in the present casepoints radially inwards and has a first surface 20 directed roughlyperpendicular to the center axis 14. In a similar manner, the secondpulling element 7 comprises a step 21 which is directed radially inwardsand has a second surface 22 that is likewise directed roughlyperpendicular to the center axis 14. The term “perpendicular” is not tobe understood in the mathematically narrow sense here. When the twosurfaces 20, 22 bear against one another, they must still be capable oftransferring a force in the pulling direction 15.

An elastic element 23, preferably a wave spring washer, annularlysurrounds the second pulling element 7. The elastic element 23 isarranged between the first step 19 of the first pulling element 6 andthe counterpart 24 which is screwed onto the second pulling element 7 orconnected to the second pulling element 7 in a different manner. Theelastic element 23 is arranged prestressed between the counterpart 24and the first step 19 without play, so that the first step 19 bears withits first surface 20 against the second surface 22 of the second step 21without play. The counterpart 24 is illustrated here as an individualelement. However, it is to be readily understood that counterpart 24 canalso be embodied or formed in one piece with the second pulling element7 or the drive device 8, or it could be composed of multiple parts.

If the drive device 8 and therefore the counterpart 24 are moved in thepulling direction 15, then the second pulling element 7 pulls the firstpulling element 6 along in the pulling direction 15 via the surfacepairing of the two surfaces 20, 22 and thus moves the chuck housing 9away from the front face 3 of the housing 2. In this manner, a settingoperation for a blind rivet fastener is performed.

After the setting operation, the chuck housing 9 is once again movedback into its initial position. Here, the movement is transferred fromthe drive device 8 to the first pulling element 6 via the elasticelement 23.

However, should debris have accumulated in an intermediate space 25between the chuck housing 9 and the front face 3 of the housing 2, whichdebris prevents a movement of the chuck housing 9 into the initialposition illustrated in FIG. 1, then the second pulling element 7 canindeed be moved all the way into the initial position illustrated inFIG. 1. However, the movement of the chuck housing 9 can be stoppedearlier, since the first pulling element 6 can come away from the secondpulling element 7, expressed more accurately, the first step 19 can comeaway from the second step 21. In this case, the elastic element 23 iscompressed. The elastic element 23 thus relieves forces which couldotherwise destroy the housing 2.

If the chuck housing 9 can no longer be moved far enough towards thenose piece 4, then the clamping jaws 10 are no longer sufficientlyopened. The user of the blind rivet setting device notices this in thata pulling mandrel of a blind rivet fastener can be inserted into theclamping jaws 10 only with difficulty or not at all, or in that itbecomes correspondingly difficult to pull a pulling mandrel out of thehousing 2. The user can then partially disassemble the housing in orderto expose the intermediate space 25 and, e.g., remove the debris locatedthere.

Since the elastic element 23 can be compressed, the length of thepulling device is variable. If the two surfaces 20, 22 bear against oneanother, then the pulling device has a first length. If the two steps19, 21 are moved relative to one another so that the two surfaces 20, 22distance themselves from one another and the elastic element 23 iscompressed, then the pulling device has a second length that is shorterthan the first length. Only when the pulling device has the first lengthare the clamping jaws 10 sufficiently opened by the nose piece 4.

The compression of the elastic element 23, and therefore the change inlength, can be small. It lies within a range of, e.g., 1 to 5 mm.

An additional solution that can also be used together with the solutionillustrated in FIG. 1 is shown in FIGS. 2 through 6. Identical andcorresponding elements are provided with the same reference numerals.

The pulling device 26 is in this case only shown from the outside.

The housing comprises a first housing part 2 a and a second housing part2 b. The first housing part 2 a is inserted into the second housing part2 b in a telescoping manner. A spring element 27 in the form of a springclip bent in a U shape is connected to the second housing part 2 b, forexample, in that it is inserted into a recess 28 that is embodied orformed in a corresponding U-shape. The spring element 27 engages in afirst circumferential groove 29 embodied or formed on the second housingpart 2 a when the blind rivet setting device 1 is ready for operation.In this case, with the two housing parts 2 a, 2 b, the housing has afirst length.

If a problem should occur during the reset movement of the pullingdevice 26, e.g., due to an accumulation of debris in the intermediatespace 25, then the first housing part 2 a is slid out of the secondhousing part 2 b in the reset direction 16 by the pulling device 26. Forthis purpose, the spring clip 27 must be pushed radially outwards out ofthe first circumferential groove 29, for which a certain force isnecessary. This force is larger than the force of the compression spring11. On the first housing part 2 a, a second circumferential groove 31can be provided, into which the spring element 27 engages again once thefirst housing part 2 a has been slightly slid out of the second housingpart 2 b. Between the two circumferential grooves 29, 31, a marking 30can be provided which indicates to a user that the second housing part 2b has moved relative to the first housing part 2 a. The marking thusshows the user that maintenance is necessary.

The spring element 27 forms a locking connection with the firstcircumferential groove 29, since a transverse clip of the spring element27 can engage in the first circumferential groove 29 when the firsthousing part 2 a is slid far enough into the second housing part 2 b. Acertain force is also necessary for this.

In a manner not illustrated in greater detail, the spring element canalso be embodied or formed as a spring clip that is inserted into thesecond housing part 2 b in a radial direction and subsequently engagesin a corresponding circumferential groove 29 on the first housing part 2a.

It is noted that the foregoing examples have been provided merely forthe purpose of explanation and are in no way to be construed as limitingof the present invention. While the present invention has been describedwith reference to an exemplary embodiment, it is understood that thewords which have been used herein are words of description andillustration, rather than words of limitation. Changes may be made,within the purview of the appended claims, as presently stated and asamended, without departing from the scope and spirit of the presentinvention in its aspects. Although the present invention has beendescribed herein with reference to particular means, materials andembodiments, the present invention is not intended to be limited to theparticulars disclosed herein; rather, the present invention extends toall functionally equivalent structures, methods and uses, such as arewithin the scope of the appended claims.

What is claimed:
 1. A blind rivet setting device comprising: a housing;a pulling device that is at least partially arranged in the housing; anda drive that acts on the pulling device in a pulling direction and in areset direction oriented opposite to the pulling direction, wherein alength of at least one of the housing and the pulling device ischangeable from a first length to a second length when a predeterminedforce is exceeded.
 2. The blind rivet setting device according to claim1, wherein the pulling device comprises a chuck housing and clampingjaws loaded into the chuck housing by a compression spring.
 3. The blindrivet setting device according to claim 2, wherein the housing comprisesa nose piece and wherein in a resting state, the clamping jaws aredisplaceable into an opened position by the nose piece when the lengthis the first length and are not displaceable into the opened positionwhen the length is the second length.
 4. The blind rivet setting deviceaccording to claim 1, wherein a difference between the first length andthe second length lies within the range of 1 to 5 mm.
 5. The blind rivetsetting device according to claim 1, wherein the pulling devicecomprises a first pulling element, a second pulling element and anelastic element that are structured and arranged so that, when thepulling device is acted on in a pulling direction, the first pullingelement and the second pulling element are positively engaged and, whenthe pulling device is acted on in the reset direction, the elasticelement acts between the first pulling element and the second pullingelement.
 6. The blind rivet setting device according to claim 5, whereinthe elastic element comprises one of a wave spring washer or otherelastomeric body.
 7. The blind rivet setting device according to claim5, wherein the first pulling element comprises a first step with a firstsurface directed crosswise to the pulling direction and the secondpulling element comprises a second step with a second surface directedcrosswise to the pulling direction, and wherein the elastic element isarranged to load the first surface and the second surface against oneanother.
 8. The blind rivet setting device according to claim 1, whereinthe housing comprises a first housing part and a second housing partthat are structured and arranged so that, in the reset direction, thefirst housing part can be displaced relative to the second housing part.9. The blind rivet setting device according to claim 8, wherein one ofthe first and second housing parts includes a marking that is visiblewhen the second length is present and not visible when the first lengthis present.
 10. The blind rivet setting device according to claim 9,wherein the first housing part and the second housing part areengageable via a locking connection.
 11. The blind rivet setting deviceaccording to claim 10, wherein the locking connection comprises at leastone spring element that is connected to one of the first and secondhousing parts and engaged with the other of the first and second housingparts in a non-positive fit.
 12. The blind rivet setting deviceaccording to claim 1, wherein the spring element comprises a springclip.
 13. A method of operating the blind rivet setting device accordingto claim 1, comprising: pulling the pulling device in the drivingdirection to move the chuck from an initial position to a position awayfrom a front face of the housing; moving the pulling device in the resetdirection to move the chuck toward the initial position; and when debrisin the housing prevents the chuck from returning to the initialposition, changing a length of at least one of the pulling device andhousing.
 14. The method according to claim 13, wherein the pullingdevice comprises a first pulling element and a second pulling elementthat are structured and arranged so that, in the driving direction, thefirst pulling element is engaged with the second pulling device so thatthe pulling device has the first length, and in the reset direction, thedebris causes the first pulling element to be displaced from the secondpulling element so that the pulling device has the second length. 15.The method according to claim 14, wherein the second length is shorterthan the first length.
 16. The method according to claim 14, the pullingdevice further comprising an elastic element arranged to return thepulling device to the first length when the debris is removed.
 17. Themethod according to claim 13, wherein the housing comprises a firsthousing part and a second housing part that are structured and arrangedso that, in the driving direction, the housing has the first length, andin the reset direction, the debris causes the first housing part to bedisplaceable relative to the second housing part so that the housing hasthe second length.
 18. The method according to claim 17, wherein thesecond length is longer than the first length.
 19. The method accordingto claim 17, wherein the housing further comprises an adjustableconnection between the first housing part and the second housing part.20. The method according to claim 17, further comprising viewing amarking on the housing to confirm that the housing has the secondlength.